/**
 * Calculate the accounting period that should be used on the approved supplier invoice, respecting
 * the per subsidiary period lock status. This is needed because this script is executed under
 * Administrator role which has "Override Period Restrictions" permission, and could potentially
 * approve invoices in a locked period if not for this check.
 *
 * See CORP-4222 for further details.
 *
 * Code is loosely based on <https://netsuite.custhelp.com/app/answers/detail/a_id/97841/>
 *
 * @param {nlobjRecord} record Invoice Record
 * @returns {string} Internal ID of the period. This will be the existing period if unlocked,
 *   otherwise the next unlocked period
 */
APApprovalSuitelet.getPostingPeriod = function (record) {
  var subsidiary = record.getFieldValue("subsidiary");
  var postingPeriod = record.getFieldValue("postingperiod");

  if (!this.isPeriodAPLockedForSubsidiary(postingPeriod, subsidiary)) {
    return postingPeriod;
  }

  var futurePeriods = this.getFutureAccountingPeriods(postingPeriod);

  for (var i = 0; i < futurePeriods.length; i++) {
    if (!this.isPeriodAPLockedForSubsidiary(futurePeriods[i], subsidiary)) {
      return futurePeriods[i];
    }
  }

  throw nlapiCreateError(
    "ERROR_CALCULATING_POSTING_PERIOD",
    "Unable to find an unlocked posting period."
  );
};

/**
 * @param {string} postingPeriod Internal ID of Account Period to Check
 * @param {string} subsidiary Internal ID of subsidiary to check
 * @returns {boolean} True if period is locked for AP transactions for given subsidiary
 */
APApprovalSuitelet.isPeriodAPLockedForSubsidiary = function (postingPeriod, subsidiary) {
  var results =
    nlapiSearchRecord(
      "taskitemstatus",
      undefined,
      [
        ["itemtype", "anyof", "PCP_LOCK_AP"],
        "AND",
        ["subsidiary", "anyof", subsidiary],
        "AND",
        ["period", "anyof", postingPeriod],
      ],
      [new nlobjSearchColumn("complete")]
    ) || [];

  if (results.length !== 1) {
    return false;
  }

  return results[0].getValue("complete") === "T";
};

/**
 * @param {string} postingPeriod Internal ID of Account Period to check from
 * @returns {string[]} Array of Internal IDs for future accounting periods that are not fully locked
 *   for AP
 */
APApprovalSuitelet.getFutureAccountingPeriods = function (postingPeriod) {
  var results =
    nlapiSearchRecord(
      "accountingperiod",
      undefined,
      [
        ["internalidnumber", "greaterthan", postingPeriod],
        "AND",
        ["aplocked", "is", "F"],
        "AND",
        ["isquarter", "is", "F"],
        "AND",
        ["isadjust", "is", "F"],
        "AND",
        ["isyear", "is", "F"],
      ],
      [new nlobjSearchColumn("internalid").setSort(false)]
    ) || [];

  var accountPeriods = results.map(function (result) {
    return result.getId();
  });

  // result has duplicates for some reason, so remove them
  return accountPeriods.filter(function (item, pos) {
    return accountPeriods.indexOf(item) === pos;
  });
};

unfortunate if WF can't change the posting period.

so would just have to return a user error, right? and also make sure to check if period is locked FIRST, otherwise you'll potentially have to undo any changes the WF makes during the approval process